With incandescent lights the current fed through its filament produces heat and light. The temperature of the filament determines the color of the light. When the temperature is low, a yellowish light is produced and as the temperature increases the light becomes whiter, like daylight. With LED's, which are semiconductor devices, they are driven by direct current and the brightness is proportional to the current flowing through the LED. Accordingly, the intensity of the LED can be controlled by controlling the amount of current fed to the LED and this is commonly controlled by a dimmer switch.
The color of light is determined in terms of color temperature expressed in Kelvin degrees. For example, sunlight in the summer is equivalent to about 5400 Kelvin temperature, warm white light is equivalent to about 3000 Kelvin temperature and light resembling a flame is equivalent to about 1700 Kelvin temperature. Accordingly, it is desirable to control the current to create a warm and cozy environment which is more relaxing than bright sunlight. It is known to mix white LED's with amber LED's and control their current to mix the color of the light generated by the combination to produce a change in the color of the light. When using different color LED's, it is common to use a driver circuit for each of the LED's or a driver with separate output channels.
Some LED light fixtures with two or more sets of color LED's, for installation in ceilings, are provided with a driver housing which is usually positioned resting on the rear surface of the ceiling sheeting with a long feed wire loose over the rear surface of the sheeting material. A switch is mounted on the driver housing to select a desired color temperature of the LED light fixture. To change the switch setting it is necessary to retract the housing by pulling the light fixture to position the driver housing adjacent the mounting hole and then with the hand to manipulate the driver housing, which is not visible, to be able to pull it out of the hole. Because the housings of LED light fixture are of different diameter sizes the fixture mounting hole may be too small to provide easy access to the drive housing and to manipulate the housing to retract it from the fixture mounting hole. This is not a task that is suitable for many people and damage can be caused to the ceiling sheeting material about the mounting hole. Still further, there is a hazard presented by the live wire connected to the driver circuit inside the driver housing, particularly if there is a fault in the wiring. There is also a hazard of working on a ladder to be close to the ceiling to remove the diver housing from the fixture mounting hole. Manipulating the driver housing is therefore not recommended for safety reasons.
In a situation where the driver housing is immovably secured to a rigid structural member at a desired location where the ceiling fixture is to be secured further problems are presented. In such an installation the user person must select the light mood desired at the time of installation has access to the switch may not be possible as it would not be visible. Also, as pointed out above, after the ceiling construction is complete the mounting hole may be too small to provide access to the driver housing. This creates a problem if the end user desires to later change the color of the light generated by the LED light fixture and such would require the skill of an electrician to do so and repair to the ceiling sheeting material, if damaged in the process.